Fan

ABSTRACT

A fan includes a nozzle and a device for creating a primary air flow through the nozzle. The nozzle includes a mouth for emitting the primary air flow, and defines a bore through which a secondary air flow from outside the fan is drawn by the primary air flow emitted from the mouth and which combines with the primary air flow to produce a combined air flow. To allow a user to adjust at least one parameter, for example at least one of the profile, orientation and the direction, of the combined air flow, the fan comprises an insert which is locatable at least partially within the bore of the nozzle. The fan may be provided with a set of such inserts.

REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 USC 371 ofInternational Application No. PCT/GB2011/051816, filed Sep. 26, 2011,which claims the priority of United Kingdom Application No. 1017706.1,filed Oct. 20, 2010, and United Kingdom Application No. 1017707.9, filedOct. 20, 2010, the entire contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a fan. Particularly, but notexclusively, the present invention relates to a floor or table-top fan,such as a desk, tower or pedestal fan.

BACKGROUND OF THE INVENTION

A conventional domestic fan typically includes a set of blades or vanesmounted for rotation about an axis, and drive apparatus for rotating theset of blades to generate an air flow. The movement and circulation ofthe air flow creates a ‘wind chill’ or breeze and, as a result, the userexperiences a cooling effect as heat is dissipated through convectionand evaporation. The blades are generally located within a cage whichallows an air flow to pass through the housing while preventing usersfrom coming into contact with the rotating blades during use of the fan.

WO 2009/030879 describes a fan assembly which does not use caged bladesto project air from the fan assembly. Instead, the fan assemblycomprises a cylindrical base which houses a motor-driven impeller fordrawing a primary air flow into the base, and an annular nozzleconnected to the base and comprising an annular mouth through which theprimary air flow is emitted from the fan. The nozzle defines an openingthrough which air in the local environment of the fan assembly is drawnby the primary air flow emitted from the mouth, amplifying the primaryair flow. The nozzle includes a Coanda surface over which the mouth isarranged to direct the primary air flow. The Coanda surface extendssymmetrically about the central axis of the opening so that the air flowgenerated by the fan assembly is in the form of an annular jet having acylindrical or frusto-conical profile.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a fan including anozzle and means for creating a primary air flow through the nozzle. Thenozzle includes at least one outlet for emitting the primary air flow,and defines a bore through which a secondary air flow from outside thefan is drawn by the primary air flow emitted from the at least oneoutlet and which combines with the primary air flow to produce acombined air flow. To allow a user to adjust at least one parameter ofthe combined air flow, the fan comprises an insert which is locatable atleast partially within the bore of the nozzle.

The at least one parameter of the combined air flow may comprise atleast one of the profile, orientation, direction, flow rate (asmeasured, for example, in litres per second), and velocity of thecombined air flow. Thus, through location of the insert within the boreof the nozzle, a user may adjust the direction in which the combined airflow is projected forward from the fan, for example to angle the airflow towards or away from a person in the vicinity of the fan.Alternatively, or additionally, the insert may expand or restrict theprofile of the combined air flow to increase or decrease the number ofusers within the path of the air flow. As another alternative the insertmay change the orientation of the air flow to provide a relatively wideair flow for cooling a number of users.

The insert may be moveable within the bore of the nozzle to allow a userto change quickly, for example the direction in which the combined airflow is projected forward from the fan. For example, the insert may beslid over and/or along the bore of the nozzle, or it may be rotatedwithin the bore of the nozzle. The nozzle may include means for guidingthe movement of the insert relative to the bore.

The insert may have any shape suitable for changing the air flow in adesired manner. For example, the insert may comprise one or moresections which are locatable within the bore of the nozzle to deflectthe combined air flow in a particular direction, for example towards oraway from a person located to one side of the fan. In one embodiment,the insert comprises a plurality of interconnected sections which arelocatable simultaneously within the bore of the nozzle. These sectionsmay have substantially the same shape, or they may have differentshapes. The sections may be wedge-shaped, tapering towards the rear endof the nozzle. The sections may be arranged about an axis. When theinsert is located within the nozzle, the insert is preferablysubstantially co-axial with the bore of the nozzle. The sections may beregularly or irregularly spaced about the axis.

The insert may be located partially within the bore of the nozzle, forexample so that part of the insert protrudes forwardly from the frontend of the nozzle to guide part or all of the combined air flow in aparticular direction. Alternatively, it may be located substantiallyfully within the bore of the nozzle. The bore of the nozzle preferablytapers outwardly towards the front end of the bore, and so the insert ispreferably inserted into the bore through the front end of the nozzle.The insert may be annular in shape. The insert may comprise a rim whichis locatable over the front edge of the nozzle to retain the insertwithin the bore of the nozzle.

The at least one outlet of the nozzle may be located towards the rear ofthe nozzle, and arranged to emit the primary air flow through the boreof the nozzle. As mentioned above, the nozzle preferably comprises asurface which defines the bore of the nozzle, and the at least oneoutlet is preferably arranged to direct the primary air flow over thesurface of the nozzle. Preferably, the surface over which the at leastone outlet is arranged to direct the primary air flow comprises a Coandasurface. A Coanda surface is a known type of surface over which fluidflow exiting an output orifice close to the surface exhibits the Coandaeffect. The fluid tends to flow over the surface closely, almost‘clinging to’ or ‘hugging’ the surface. The Coanda effect is already aproven, well documented method of entrainment in which a primary airflow is directed over a Coanda surface. A description of the features ofa Coanda surface, and the effect of fluid flow over a Coanda surface,can be found in articles such as Reba, Scientific American, Volume 214,June 1966 pages 84 to 92. Through use of a Coanda surface, an increasedamount of air from outside the fan is drawn through the bore by the airemitted from the nozzle.

In a preferred embodiment an air flow is created through the nozzle ofthe fan. In the following description this air flow will be referred toas the primary air flow. The primary air flow is emitted from the atleast one outlet of the nozzle and preferably passes over a Coandasurface. The primary air flow entrains air surrounding the nozzle, whichacts as an air amplifier to supply both the primary air flow and theentrained air to the user. The entrained air will be referred to here asa secondary air flow. The secondary air flow is drawn from the roomspace, region or external environment surrounding the mouth of thenozzle and, by displacement, from other regions around the fan, andpasses predominantly through the bore defined by the nozzle. The primaryair flow directed over the Coanda surface combined with the entrainedsecondary air flow equates to a combined, or total, air flow emitted orprojected forward from the front end of the bore of the nozzle.

The Coanda surface may comprise a diffuser portion located downstreamfrom the at least one outlet. The diffuser portion preferably extendsabout an axis, and preferably tapers towards or away from the axis.

The insert preferably covers at least part of the Coanda surface of thenozzle, and so may be provided in the form of a mask which is insertableinto the bore of the nozzle. The insert preferably covers at least partof the diffuser portion of the Coanda surface. Where the insertcomprises a plurality of interconnected sections, each section may covera respective part of the diffuser portion of the Coanda surface.

As an alternative to providing the insert with a number ofinterconnected sections, the insert may comprise a surface defining abore through which, when the insert is located in the nozzle, thesecondary air flow from outside the fan is drawn by the primary air flowemitted from the mouth. This insert can cover an annular section of theCoanda surface, preferably at least part of the diffuser portion of theCoanda surface and more preferably substantially all of the diffuserportion of the Coanda surface. When the insert is located within thenozzle, the bore of the insert is preferably substantially co-axial withthe bore of the nozzle. The at least one outlet of the nozzle ispreferably arranged to direct the primary air flow through the bore ofthe insert.

The surface of the insert preferably extends about an axis, and at leastpart of that surface is preferably inclined to that axis. Theinclination of the surface of the insert to the axis is preferablydifferent from the inclination of the diffuser portion of the Coandasurface. In this case, the location of the insert within the bore of thenozzle can change the flow rate and the velocity of the combined airflow. For example where the angle by which the surface of the insert isinclined to the axis is shallower than the angle by which the diffuserportion of the Coanda surface is inclined to the axis, the flow rate ofthe combined air flow will decrease when the insert is located withinthe nozzle, but the velocity of the combined air flow will increase.

Substantially all of the surface of the insert may be inclined to theaxis by the same amount, and so the surface may have a shape which iscylindrical or frusto-conical. The angle of inclination may be in therange from −15 to 35°. Alternatively, the angle of inclination may varyabout the axis. Through varying the angle of inclination about the axis,the air current generated by the fan may have a non-cylindrical or anon-frusto-conical profile when the insert is located within the bore ofthe nozzle. The angle may vary along the surface, that is, about theaxis, between at least one maximum value and at least one minimum value.Preferably, the angle varies along the surface between a plurality ofmaximum values and a plurality of minimum values. In a preferredembodiment the angle varies along the surface between six maximum valuesand six minimum values. The maximum values and the minimum values arepreferably regularly spaced about the axis. The minimum value may be inthe range from −15° to 15°, whereas the maximum value may be in therange from 20 to 35°. In a preferred embodiment the maximum value is atleast twice the minimum value. The angle of inclination may varycontinuously or discontinuously about the axis.

The fan may comprise a set of inserts which are interchangeablylocatable within the bore of the nozzle, and so in a second aspect thepresent invention provides a fan comprising a nozzle and means forcreating a primary air flow through the nozzle, the nozzle comprising atleast one outlet for emitting the primary air flow, the nozzle defininga bore through which a secondary air flow from outside the fan is drawnby the primary air flow emitted from the at least one outlet and whichcombines with the primary air flow to produce a combined air flow;characterised in that the fan comprises a plurality of insertsinsertable interchangeably into the bore of the nozzle for adjusting atleast one parameter of the combined air flow, each insert having arespective different profile. For example, as discussed above one of theinserts may comprise a plurality of interconnected sections, whereasanother one of the inserts may comprise a bore through the secondary airflow is drawn by the emission of the primary air flow from the mouth ofthe nozzle.

The at least one outlet preferably extends about the bore of the nozzle.The nozzle may comprise a single outlet which is continuous about thebore, and may be substantially circular in shape. Preferably, thespacing between opposing surfaces of the nozzle at the outlet(s) ispreferably in the range from 0.5 mm to 5 mm. The, or each, outlet ispreferably in the form of a slot.

The nozzle is preferably mounted on a base housing said means forcreating an air flow. In the preferred fan the means for creating an airflow through the nozzle comprises an impeller driven by a motor.

The insert may be provided separately from the fan, and so in a thirdaspect the present invention provides an accessory for a fan comprisinga nozzle having at least one outlet for emitting a primary air flow anda bore through which a secondary air flow from outside the fan is drawnby the primary air flow emitted from the at least one outlet and whichcombines with the primary air flow to produce a combined air flow, theaccessory being locatable on the nozzle, preferably within the bore ofthe nozzle.

As mentioned above, the accessory may change at least one parameter ofthe combined air flow. However, the accessory may provide alternative,or additional, benefits for the user. For example, the accessory mayhave a different colour to the nozzle of the fan, and/or may be formedfrom a different material to the nozzle of the fan. The accessory may beformed from luminous material, or may comprise one or more lightemitting diodes (LEDs) or other illuminating means. The accessory may beconfigured to support a picture, photo or other item(s). For example,the accessory may comprise a housing for retaining one or more items,such as items of stationery, money, keys, a remote control and the like.The accessory may clip on to the front end of the nozzle. The accessorymay comprise a thermometer, a barometer, a camera, a display, a clock, aradio or other electronic or mechanical device.

In a fourth aspect the present invention provides a fan comprising anozzle and means for creating an air flow through the nozzle, the nozzlecomprising an interior passage, at least one outlet for receiving theair flow from the interior passage, and a Coanda surface locatedadjacent the at least one outlet and over which the at least one outletis arranged to direct the air flow, characterised in that the fancomprises a removable mask for covering at least part of the Coandasurface.

Features described above in connection with the first aspect of theinvention are equally applicable to the second to fourth aspects of theinvention, and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features of the invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a front perspective view, from above, of a fan;

FIG. 2 is a side sectional view through the fan;

FIG. 3 is a front perspective view, from above, of an insert for thefan;

FIG. 4 is a front perspective view, from above, of the fan with theinsert located in the bore of the nozzle;

FIG. 5 is a side view of the fan of FIG. 4;

FIG. 6 is a top view of the fan of FIG. 4;

FIG. 7 is a front view of the fan of FIG. 4;

FIG. 8 is a side sectional view taken along line A-A in FIG. 7;

FIG. 9 is a front perspective view, from above, of a second insert forthe fan;

FIG. 10 is a front perspective view, from above, of the fan with thesecond insert located in the bore of the nozzle;

FIG. 11 is a front perspective view, from above, of a third insert forthe fan; and

FIG. 12 is a front perspective view, from above, of the fan with thethird insert located in the bore of the nozzle.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is an external view of a fan 10. The fan 10 comprises a body 12comprising an air inlet 14 through which a primary air flow enters thefan 10, and a nozzle 16 in the form of an annular casing mounted on thebody 12, and which comprises a mouth 18 for emitting the primary airflow from the fan 10.

The body 12 comprises a substantially cylindrical main body section 20mounted on a substantially cylindrical lower body section 22. The mainbody section 20 and the lower body section 22 preferably havesubstantially the same external diameter so that the external surface ofthe upper body section 20 is substantially flush with the external 5.surface of the lower body section 22. In this embodiment the body 12 hasa height in the range from 100 to 300 mm, and a diameter in the rangefrom 100 to 200 mm.

The main body section 20 comprises the air inlet 14 through which theprimary air flow enters the fan 10. In this embodiment the air inlet 14comprises an array of apertures formed in the main body section 20.Alternatively, the air inlet 14 may comprise one or more grilles ormeshes mounted within windows formed in the main body section 20. Themain body section 20 is open at the upper end (as illustrated) thereofto provide an air outlet 23 through which the primary air flow isexhausted from the body 12.

The main body section 20 may be tilted relative to the lower bodysection 22 to adjust the direction in which the primary air flow isemitted from the fan 10. For example, the upper surface of the lowerbody section 22 and the lower surface of the main body section 20 may beprovided with interconnecting features which allow the main body section20 to move relative to the lower body section 22 while preventing themain body section 20 from being lifted from the lower body section 22.For example, the lower body section 22 and the main body section 20 maycomprise interlocking L-shaped members.

The lower body section 22 comprises a user interface of the fan 10. Theuser interface comprises a plurality of user-operable buttons 24, 26, adial 28 for enabling a user to control various functions of the fan 10,and user interface control circuit 30 connected to the buttons 24, 26and the dial 28. The lower body section 22 is mounted on a base 32 forengaging a surface on which the fan 10 is located.

FIG. 2 illustrates a sectional view through the body of the fan 10. Thelower body section 22 houses a main control circuit, indicated generallyat 34, connected to the user interface control circuit 30. In responseto operation of the buttons 24, 26 and the dial 28, the user interfacecontrol circuit 30 is arranged to transmit appropriate signals to themain control circuit 34 to control various operations of the fan 10.

The lower body section 22 also houses a mechanism, indicated generallyat 36, for oscillating the lower body section 22 relative to the base32. The operation of the oscillating mechanism 36 is controlled by themain control circuit 34 in response to the user operation of the button26. The range of each oscillation cycle of the lower body section 22relative to the base 32 is preferably between 60° and 120°, and in thisembodiment is around 80°. In this embodiment, the oscillating mechanism36 is arranged to perform around 3 to 5 oscillation cycles per minute. Amains power cable 38 for supplying electrical power to the fan 10extends through an aperture formed in the base 32. The cable 38 isconnected to a plug (not shown) for connection to a mains power supply.

The main body section 20 houses an impeller 40 for drawing the primaryair flow through the air inlet 14 and into the body 12. Preferably, theimpeller 40 is in the form of a mixed flow impeller. The impeller 40 isconnected to a rotary shaft 42 extending outwardly from a motor 44. Inthis embodiment, the motor 44 is a DC brushless motor having a speedwhich is variable by the main control circuit 34 in response to usermanipulation of the dial 28. The maximum speed of the motor 44 ispreferably in the range from 5,000 to 10,000 rpm. The motor 44 is housedwithin a motor bucket comprising an upper portion 46 connected to alower portion 48. The upper portion 46 of the motor bucket comprises adiffuser 50 in the form of a stationary disc having spiral blades.

The motor bucket is located within, and mounted on, a generallyfrusto-conical impeller housing 52. The impeller housing 52 is, in turn,mounted on a plurality of angularly spaced supports 54, in this examplethree supports, located within and connected to the main body section 20of the base 12. The impeller 40 and the impeller housing 52 are shapedso that the impeller 40 is in close proximity to, but does not contact,the inner surface of the impeller housing 52. A substantially annularinlet member 56 is connected to the bottom of the impeller housing 52for guiding the primary air flow into the impeller housing 52. Anelectrical cable 58 passes from the main control circuit 34 to the motor44 through apertures formed in the main body section 20 and the lowerbody section 22 of the body 12, and in the impeller housing 52 and themotor bucket.

Preferably, the body 12 includes silencing foam for reducing noiseemissions from the body 12. In this embodiment, the main body section 20of the body 12 comprises a first foam member 60 located beneath the airinlet 14, and a second annular foam member 62 located within the motorbucket.

A flexible sealing member 64 is mounted on the impeller housing 52. Theflexible sealing member prevents air from passing around the outersurface of the impeller housing 52 to the inlet member 56. The sealingmember 64 preferably comprises an annular lip seal, preferably formedfrom rubber. The sealing member 64 further comprises a guide portion inthe form of a grommet for guiding the electrical cable 58 to the motor44.

Returning to FIG. 1, the nozzle 16 has an annular shape, extending abouta central axis X to define a bore 70. The mouth 18 is located towardsthe rear of the nozzle 16, and is arranged to emit the primary air flowtowards the front of the fan 10, through the bore 70. The mouth 18surrounds the bore 70. In this example, the nozzle 16 defines agenerally circular bore 70 extending along the central axis X. Theinnermost, external surface of the nozzle 16 comprises a Coanda surface72 located adjacent the mouth 18, and over which the mouth 18 isarranged to direct the air emitted from the fan 10. The Coanda surface72 comprises a diffuser portion 74 tapering away from the central axisX. In this example, the diffuser portion 74 is in the form of agenerally frusto-conical surface extending about the axis X, and whichis inclined to the axis X at an angle in the range from 5 to 35°, and inthis example is around 28°.

The nozzle 16 comprises an annular front casing section 76 connected toand extending about an annular rear casing section 78. The annularsections 76, 78 of the nozzle 16 extend about the central axis X. Eachof these sections may be formed from a plurality of connected parts, butin this embodiment each of the front casing section 76 and the rearcasing section 78 is formed from a respective, single moulded part. Therear casing section 78 comprises a base 80 which is connected to theopen upper end of the main body section 20 of the body 12, and which hasan open lower end for receiving the primary air flow from the body 12.

With reference also to FIG. 2, during assembly, the front end 82 of therear casing section 78 is inserted into a slot 84 located in the frontcasing section 76. Each of the front end 82 and the slot 84 is generallycylindrical. The casing sections 76, 78 may be connected together usingan adhesive introduced to the slot 84.

The front casing section 76 defines the Coanda surface 72 of the nozzle16. The front casing section 76 and the rear casing section 78 togetherdefine an annular interior passage 88 for conveying the primary air flowto the mouth 18. The interior passage 88 extends about the axis X, andis bounded by the internal surface 90 of the front casing section 76 andthe internal surface 92 of the rear casing section 78. The base 80 ofthe front casing section 76 is shaped to convey the primary air flowinto the interior passage 88 of the nozzle 16.

The mouth 18 is defined by overlapping, or facing, portions of theinternal surface 92 of the rear casing section 78 and the externalsurface 94 of the front casing section 76, respectively. The mouth 18preferably comprises an air outlet in the form of an annular slot. Theslot is preferably generally circular in shape, and preferably has arelatively constant width in the range from 0.5 to 5 mm. In this examplethe air outlet has a width of around 1 mm. Spacers may be spaced aboutthe mouth 18 for urging apart the overlapping portions of the frontcasing section 76 and the rear casing section 78 to control the width ofthe air outlet of the mouth 18. These spacers may be integral witheither the front casing section 76 or the rear casing section 78. Themouth 18 is shaped to direct the primary air flow over the externalsurface 94 of the front casing section 76.

To operate the fan 10 the user the user presses button 24 of the userinterface. The user interface control circuit 30 communicates thisaction to the main control circuit 34, in response to which the maincontrol circuit 34 activates the motor 44 to rotate the impeller 40. Therotation of the impeller 40 causes a primary air flow to be drawn intothe body 12 through the air inlet 14. The user may control the speed ofthe motor 44, and therefore the rate at which air is drawn into the body12 through the air inlet 14, by manipulating the dial 28 of the userinterface. Depending on the speed of the motor 44, the primary air flowgenerated by the impeller 40 may be between 10 and 30 litres per second.The primary air flow passes sequentially through the impeller housing 52and the air outlet 23 at the open upper end of the main body portion 20to enter the interior passage 88 of the nozzle 16. The pressure of theprimary air flow at the air outlet 23 of the body 12 may be at least 150Pa, and is preferably in the range from 250 to 1.5 kPa.

Within the interior passage 88 of the nozzle 16, the primary air flow isdivided into two air streams which pass in opposite directions aroundthe bore 70 of the nozzle 16. As the air streams pass through theinterior passage 70, air is emitted through the mouth 18. The primaryair flow emitted from the mouth 18 is directed over the Coanda surface72 of the nozzle 16, causing a secondary air flow to be generated by theentrainment of air from the external environment, specifically from theregion around the mouth 18 and from around the rear of the nozzle 16.This secondary air flow passes through the bore 70 of the nozzle 16,where it combines with the primary air flow to produce a combined, ortotal, air flow, or air current, projected forward from the nozzle 16.

With reference now also to FIGS. 3 to 8, the fan 10 includes a firstexample of a mask 100 which is removably locatable over the Coandasurface 72 of the nozzle to change at least one parameter of thecombined air flow. The mask 100 is in the form of an insert which isinsertable into the bore 70 of the nozzle 16 to cover at least part ofthe Coanda surface 72 of the nozzle 16. As the diffuser portion 74 ofthe Coanda surface 72, and thus the bore 70, tapers outwardly towardsthe open front end 96 of the bore 70, the mask 100 is inserted into thebore 70 of the nozzle 16 through the open front end 96 of the bore 70.The mask 100 includes an outer annular rim 102 which is locatable overthe front end 96 of the bore 70, and which surrounds the outer surfaceof the front casing section 76 of the nozzle 16 when the mask 100 islocated on the nozzle 16. In this example the mask 100 is retained onthe nozzle 16 through an interference fit between the nozzle 16 and themask 100, but the nozzle 16 may be provided with means for removablysecuring the mask 100 to the nozzle 16. For example, a movable catch maybe located on the outer surface of the front casing section 76 of thenozzle 16 to retain the mask 100 on the nozzle 16. As another example,the mask 100 may be attracted magnetically to the nozzle 16. As afurther example, the mask 100 may be frictionally coupled to the nozzle16.

To remove the mask 100, the user may simply pull the mask 100 from thenozzle 16.

The mask 100 is generally annular in shape. The mask 100 comprises agenerally circular front end 104 and a generally circular rear end 106,and an annular outer surface 108 and an annular inner surface 110 whicheach extend between the front end 104 and the rear end 106 of the mask100. Each of the outer surface 108 and the inner surface 110 of the mask100 extend about an axis Y, which, with reference to FIG. 2, issubstantially co-linear with the axis X of the nozzle 16 when the mask100 is inserted into the bore 70 of the nozzle 16. The outer surface 108of the mask 100 has generally the same size and shape as the diffuserportion 74 of the Coanda surface. In particular, the angle ofinclination of the outer surface 108 to the axis Y is substantially thesame as the angle of inclination of the diffuser portion 74 of theCoanda surface 72 to the axis X, Consequently, and as shown in FIG. 8,when the mask 100 is inserted into the bore 70 of the nozzle 16 thediffuser portion 74 of the Coanda surface 72 is fully covered by themask 100, but the mouth 18 of the nozzle 16 remains fully exposed.

Thus, when the mask 100 is inserted into the bore 70 the primary airflow emitted from the nozzle 16 is directed over the rear section 73 ofthe Coanda surface 72, as indicated in FIG. 8, and over the innersurface 110 of the mask 100. As mentioned above, the inner surface 110of the mask 100 is annular in shape, and so defines a bore 112 passingthrough the mask 100 between the front end 104 and the rear end 106 ofthe mask 100, and through which a secondary air flow from outside thefan 10 is drawn by the primary air flow emitted from the mouth 18.

The inner surface 110 of the mask 100 thus provides a diffuser surfacefor guiding the combined air flow generated by the fan 10 in a desireddirection. The angle of inclination of the inner surface 110 to the axisY is different from the angle of inclination of the diffuser portion 74of the Coanda surface 72 to the axis X, and so the result of insertingthe mask 100 into the bore 70 of the nozzle 16 is that a number ofparameters of the combined air flow are changed. In this example, theangle of inclination of the inner surface 110 to the axis Y is shallowerthan the angle of inclination of the diffuser portion 74 of the Coandasurface 72 to the axis X, and so the radial thickness of the mask 100decreases towards the rear end 106 of the mask 100. In this example theangle of inclination of the inner surface 110 to the axis Y is around10°, and so the insertion of the mask 100 into the bore 70 of the nozzle16 serves to constrict the profile of the combined air flow produced bythe fan 10. This can provide a combined air flow which is focussedtowards a user located in front of the fan 10. The shallower diffuserportion provided by the mask 100 also serves to increase the velocity ofthe combined air flow, and to decrease the flow rate of the combined airflow.

FIGS. 9 and 10 illustrate a second example of a mask 120 which isremovably locatable over the Coanda surface 72 of the nozzle to changeat least one parameter of the combined air flow. Similar to the mask100, the mask 120 is also in the form of an insert which is insertableinto the bore 70 of the nozzle 16 to cover at least part of the Coandasurface 72 of the nozzle 16. The mask 120 also includes an outer annularrim 122 which is locatable over the front end 96 of the bore 70, andwhich surrounds the outer surface of the front casing section 76 of thenozzle 16 when the mask 100 is located on the nozzle 16. However, thismask 120 varies from the mask 100 insofar as the front end 124, rear end126, outer surface 128 and inner surface 130 of the mask 120 are notcontinuous. Instead, the mask 120 comprises a plurality of sections 132which are connected by the annular rim 122, and which are located about,and generally regularly spaced about, the axis Y of the mask 120. Inthis example, the mask 120 comprises six sections 130 regularly spacedabout the mask 120. Each section 132 is generally wedge-shaped. Theouter surfaces 128 each taper towards the axis Y with the same angle ofinclination as that between the diffuser portion 74 of the Coandasurface 72 and the axis X so that, when the mask 120 is located on thenozzle 16, the sections 132 of the mask 120 partially cover the diffuserportion 74 of the Coanda surface 72. Similar to the inner surface 110 ofthe mask 100, the angle of inclination of the inner surfaces 130 to theaxis Y is shallower than the angle of inclination of the diffuserportion 74 of the Coanda surface 72 to the axis X, and so the radialthickness of the sections 132 decreases towards the rear ends 126 of thesections 130. In this example the angle of inclination of the innersurfaces 130 to the axis Y is also around 10°.

Thus, as illustrated in FIG. 9, when the mask 120 is inserted into thenozzle 16 through the open front end 96 of the bore 70, the bore 134 ofthe nozzle 16 is defined both by the uncovered sections of the diffuserportion 74 of the Coanda surface 72, and by the inner surfaces 130 ofthe mask 120. The bore 134 of the nozzle 126 thus has a stepped profile,in which the angle of inclination of the bore 134 to the axis X variesbetween a plurality of maximum values, in this example each at around28°, and a plurality of minimum values, in this example each at around10°. This variation in the profile of the bore 134 of the nozzle 16causes the combined air flow to have a non-circular, ornon-frusto-conical, profile which is only partially focussed towards theuser due to the discontinuities in the mask 120.

In this second example, the insertion of the mask 120 into the nozzle 16results in the bore 134 of the nozzle 16 adopting a stepped profile.FIGS. 11 and 12 illustrate a third example of a mask 140. This mask 140is similar to the mask 100. The mask 140 is also in the form of aninsert which is insertable into the bore 70 of the nozzle 16 to cover atleast part of the Coanda surface 72 of the nozzle 16. The mask 140 alsoincludes an outer annular rim 142 which is locatable over the front end96 of the bore 70, and which surrounds the outer surface of the frontcasing section 76 of the nozzle 16 when the mask 100 is located on thenozzle 16. The mask 140 also has a continuous front end 144, and acircular rear end 146, an annular outer surface 148 and an annular innersurface 150 which defines a bore 152. The outer surface 148 of the mask140 is identical to the outer surface 108 of the mask 100. However, theinner surface 150 of the mask 140 differs from the inner surface 110 ofthe mask 100 insofar as the angle of inclination of the inner surface150 to the axis Y of the mask 140 varies about the axis Y. This angle ofinclination varies between a plurality of maximum values and a pluralityof minimum values which are regularly spaced about the axis Y. The innersurface 150 is shaped so as to vary the angle of inclination graduallyabout the axis Y between the maximum and minimum values.

Thus, when the mask 140 is inserted into the bore 70 of the nozzle 16,the inner surface 150 of the mask 140 also provides a diffuser surfacefor guiding the combined air flow generated by the fan 10 so as to adopta non-circular or non-frusto-conical profile. Similar also to the mask120, the mask 140 is rotatable relative to the nozzle 16 to change theorientation of the combined air flow generated by the fan.

1. A fan comprising a nozzle and a device for creating a primary airflow through the nozzle, the nozzle comprising at least one outlet foremitting the primary air flow, the nozzle defining a bore through whicha secondary air flow from outside the fan is drawn by the primary airflow emitted from the at least one outlet and which combines with theprimary air flow to produce a combined air flow, wherein the fancomprises an insert locatable at least partially within the bore of thenozzle for adjusting at least one parameter of the combined air flow. 2.The fan of claim 1, wherein the insert is rotatable within the bore ofthe nozzle.
 3. The fan of claim 1, wherein the insert is annular inshape.
 4. The fan of claim 1, wherein the insert comprises a rim whichis locatable over a front end of the nozzle.
 5. The fan of claim 1,wherein the insert tapers towards a rear end thereof.
 6. The fan ofclaim 1, wherein the insert comprises a surface defining a bore throughwhich, when the insert is located in the nozzle, the secondary air flowfrom outside the fan is drawn by the primary air flow emitted from theat least one outlet.
 7. The fan of claim 6, wherein, when the insert islocated within the nozzle, the bore of the insert is substantiallyco-axial with the bore of the nozzle.
 8. The fan of claim 6, wherein,when the insert is located within the nozzle, the at least one outlet ofthe nozzle is arranged to direct the primary air flow through the boreof the insert.
 9. The fan of claim 6, wherein the surface extends aboutan axis.
 10. The fan of claim 9, wherein at least part of the surface isinclined to the axis.
 11. The fan of claim 10, wherein the angle bywhich said at least part of the surface is inclined to the axis variesabout the axis.
 12. The fan of claim 10, wherein the angle by which saidat least part of the surface is inclined to the axis varies continuouslyabout the axis.
 13. The fan of claim 6, wherein the surface iscontinuous about the axis.
 14. The fan of claim 1, wherein the insertcomprises a plurality of interconnected sections which are locatablesimultaneously within the bore of the nozzle.
 15. The fan of claim 14,wherein the sections have substantially the same shape.
 16. The fan ofclaim 14, wherein the sections are substantially wedge shaped.
 17. Thefan of claim 14, wherein the sections are arranged about an axis. 18.The fan of claim 17, wherein the sections are regularly spaced about theaxis.
 19. The fan of claim 14, wherein each of the sections comprises asurface which is inclined to the axis.
 20. The fan of claim 19, whereinthe at least one outlet of the nozzle is arranged to direct the primaryair flow over the surfaces of the sections of the insert.
 21. The fan ofclaim 1, wherein said at least one parameter of the combined air flowcomprises at least one of the profile, orientation, direction, flow rateand velocity of the combined air flow.
 22. The fan of claim 1, whereinthe at least one outlet extends about the bore.
 23. The fan of claim 1,wherein the at least one outlet is in the form of a slot.
 24. (canceled)